1 /* 2 * fs/signalfd.c 3 * 4 * Copyright (C) 2003 Linus Torvalds 5 * 6 * Mon Mar 5, 2007: Davide Libenzi <davidel@xmailserver.org> 7 * Changed ->read() to return a siginfo strcture instead of signal number. 8 * Fixed locking in ->poll(). 9 * Added sighand-detach notification. 10 * Added fd re-use in sys_signalfd() syscall. 11 * Now using anonymous inode source. 12 * Thanks to Oleg Nesterov for useful code review and suggestions. 13 * More comments and suggestions from Arnd Bergmann. 14 * Sat May 19, 2007: Davi E. M. Arnaut <davi@haxent.com.br> 15 * Retrieve multiple signals with one read() call 16 * Sun Jul 15, 2007: Davide Libenzi <davidel@xmailserver.org> 17 * Attach to the sighand only during read() and poll(). 18 */ 19 20 #include <linux/file.h> 21 #include <linux/poll.h> 22 #include <linux/init.h> 23 #include <linux/fs.h> 24 #include <linux/sched.h> 25 #include <linux/slab.h> 26 #include <linux/kernel.h> 27 #include <linux/signal.h> 28 #include <linux/list.h> 29 #include <linux/anon_inodes.h> 30 #include <linux/signalfd.h> 31 #include <linux/syscalls.h> 32 #include <linux/proc_fs.h> 33 34 void signalfd_cleanup(struct sighand_struct *sighand) 35 { 36 wait_queue_head_t *wqh = &sighand->signalfd_wqh; 37 /* 38 * The lockless check can race with remove_wait_queue() in progress, 39 * but in this case its caller should run under rcu_read_lock() and 40 * sighand_cachep is SLAB_DESTROY_BY_RCU, we can safely return. 41 */ 42 if (likely(!waitqueue_active(wqh))) 43 return; 44 45 /* wait_queue_t->func(POLLFREE) should do remove_wait_queue() */ 46 wake_up_poll(wqh, POLLHUP | POLLFREE); 47 } 48 49 struct signalfd_ctx { 50 sigset_t sigmask; 51 }; 52 53 static int signalfd_release(struct inode *inode, struct file *file) 54 { 55 kfree(file->private_data); 56 return 0; 57 } 58 59 static unsigned int signalfd_poll(struct file *file, poll_table *wait) 60 { 61 struct signalfd_ctx *ctx = file->private_data; 62 unsigned int events = 0; 63 64 poll_wait(file, ¤t->sighand->signalfd_wqh, wait); 65 66 spin_lock_irq(¤t->sighand->siglock); 67 if (next_signal(¤t->pending, &ctx->sigmask) || 68 next_signal(¤t->signal->shared_pending, 69 &ctx->sigmask)) 70 events |= POLLIN; 71 spin_unlock_irq(¤t->sighand->siglock); 72 73 return events; 74 } 75 76 /* 77 * Copied from copy_siginfo_to_user() in kernel/signal.c 78 */ 79 static int signalfd_copyinfo(struct signalfd_siginfo __user *uinfo, 80 siginfo_t const *kinfo) 81 { 82 long err; 83 84 BUILD_BUG_ON(sizeof(struct signalfd_siginfo) != 128); 85 86 /* 87 * Unused members should be zero ... 88 */ 89 err = __clear_user(uinfo, sizeof(*uinfo)); 90 91 /* 92 * If you change siginfo_t structure, please be sure 93 * this code is fixed accordingly. 94 */ 95 err |= __put_user(kinfo->si_signo, &uinfo->ssi_signo); 96 err |= __put_user(kinfo->si_errno, &uinfo->ssi_errno); 97 err |= __put_user((short) kinfo->si_code, &uinfo->ssi_code); 98 switch (kinfo->si_code & __SI_MASK) { 99 case __SI_KILL: 100 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 101 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 102 break; 103 case __SI_TIMER: 104 err |= __put_user(kinfo->si_tid, &uinfo->ssi_tid); 105 err |= __put_user(kinfo->si_overrun, &uinfo->ssi_overrun); 106 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 107 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 108 break; 109 case __SI_POLL: 110 err |= __put_user(kinfo->si_band, &uinfo->ssi_band); 111 err |= __put_user(kinfo->si_fd, &uinfo->ssi_fd); 112 break; 113 case __SI_FAULT: 114 err |= __put_user((long) kinfo->si_addr, &uinfo->ssi_addr); 115 #ifdef __ARCH_SI_TRAPNO 116 err |= __put_user(kinfo->si_trapno, &uinfo->ssi_trapno); 117 #endif 118 #ifdef BUS_MCEERR_AO 119 /* 120 * Other callers might not initialize the si_lsb field, 121 * so check explicitly for the right codes here. 122 */ 123 if (kinfo->si_code == BUS_MCEERR_AR || 124 kinfo->si_code == BUS_MCEERR_AO) 125 err |= __put_user((short) kinfo->si_addr_lsb, 126 &uinfo->ssi_addr_lsb); 127 #endif 128 break; 129 case __SI_CHLD: 130 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 131 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 132 err |= __put_user(kinfo->si_status, &uinfo->ssi_status); 133 err |= __put_user(kinfo->si_utime, &uinfo->ssi_utime); 134 err |= __put_user(kinfo->si_stime, &uinfo->ssi_stime); 135 break; 136 case __SI_RT: /* This is not generated by the kernel as of now. */ 137 case __SI_MESGQ: /* But this is */ 138 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 139 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 140 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 141 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 142 break; 143 default: 144 /* 145 * This case catches also the signals queued by sigqueue(). 146 */ 147 err |= __put_user(kinfo->si_pid, &uinfo->ssi_pid); 148 err |= __put_user(kinfo->si_uid, &uinfo->ssi_uid); 149 err |= __put_user((long) kinfo->si_ptr, &uinfo->ssi_ptr); 150 err |= __put_user(kinfo->si_int, &uinfo->ssi_int); 151 break; 152 } 153 154 return err ? -EFAULT: sizeof(*uinfo); 155 } 156 157 static ssize_t signalfd_dequeue(struct signalfd_ctx *ctx, siginfo_t *info, 158 int nonblock) 159 { 160 ssize_t ret; 161 DECLARE_WAITQUEUE(wait, current); 162 163 spin_lock_irq(¤t->sighand->siglock); 164 ret = dequeue_signal(current, &ctx->sigmask, info); 165 switch (ret) { 166 case 0: 167 if (!nonblock) 168 break; 169 ret = -EAGAIN; 170 default: 171 spin_unlock_irq(¤t->sighand->siglock); 172 return ret; 173 } 174 175 add_wait_queue(¤t->sighand->signalfd_wqh, &wait); 176 for (;;) { 177 set_current_state(TASK_INTERRUPTIBLE); 178 ret = dequeue_signal(current, &ctx->sigmask, info); 179 if (ret != 0) 180 break; 181 if (signal_pending(current)) { 182 ret = -ERESTARTSYS; 183 break; 184 } 185 spin_unlock_irq(¤t->sighand->siglock); 186 schedule(); 187 spin_lock_irq(¤t->sighand->siglock); 188 } 189 spin_unlock_irq(¤t->sighand->siglock); 190 191 remove_wait_queue(¤t->sighand->signalfd_wqh, &wait); 192 __set_current_state(TASK_RUNNING); 193 194 return ret; 195 } 196 197 /* 198 * Returns a multiple of the size of a "struct signalfd_siginfo", or a negative 199 * error code. The "count" parameter must be at least the size of a 200 * "struct signalfd_siginfo". 201 */ 202 static ssize_t signalfd_read(struct file *file, char __user *buf, size_t count, 203 loff_t *ppos) 204 { 205 struct signalfd_ctx *ctx = file->private_data; 206 struct signalfd_siginfo __user *siginfo; 207 int nonblock = file->f_flags & O_NONBLOCK; 208 ssize_t ret, total = 0; 209 siginfo_t info; 210 211 count /= sizeof(struct signalfd_siginfo); 212 if (!count) 213 return -EINVAL; 214 215 siginfo = (struct signalfd_siginfo __user *) buf; 216 do { 217 ret = signalfd_dequeue(ctx, &info, nonblock); 218 if (unlikely(ret <= 0)) 219 break; 220 ret = signalfd_copyinfo(siginfo, &info); 221 if (ret < 0) 222 break; 223 siginfo++; 224 total += ret; 225 nonblock = 1; 226 } while (--count); 227 228 return total ? total: ret; 229 } 230 231 #ifdef CONFIG_PROC_FS 232 static int signalfd_show_fdinfo(struct seq_file *m, struct file *f) 233 { 234 struct signalfd_ctx *ctx = f->private_data; 235 sigset_t sigmask; 236 237 sigmask = ctx->sigmask; 238 signotset(&sigmask); 239 render_sigset_t(m, "sigmask:\t", &sigmask); 240 241 return 0; 242 } 243 #endif 244 245 static const struct file_operations signalfd_fops = { 246 #ifdef CONFIG_PROC_FS 247 .show_fdinfo = signalfd_show_fdinfo, 248 #endif 249 .release = signalfd_release, 250 .poll = signalfd_poll, 251 .read = signalfd_read, 252 .llseek = noop_llseek, 253 }; 254 255 SYSCALL_DEFINE4(signalfd4, int, ufd, sigset_t __user *, user_mask, 256 size_t, sizemask, int, flags) 257 { 258 sigset_t sigmask; 259 struct signalfd_ctx *ctx; 260 261 /* Check the SFD_* constants for consistency. */ 262 BUILD_BUG_ON(SFD_CLOEXEC != O_CLOEXEC); 263 BUILD_BUG_ON(SFD_NONBLOCK != O_NONBLOCK); 264 265 if (flags & ~(SFD_CLOEXEC | SFD_NONBLOCK)) 266 return -EINVAL; 267 268 if (sizemask != sizeof(sigset_t) || 269 copy_from_user(&sigmask, user_mask, sizeof(sigmask))) 270 return -EINVAL; 271 sigdelsetmask(&sigmask, sigmask(SIGKILL) | sigmask(SIGSTOP)); 272 signotset(&sigmask); 273 274 if (ufd == -1) { 275 ctx = kmalloc(sizeof(*ctx), GFP_KERNEL); 276 if (!ctx) 277 return -ENOMEM; 278 279 ctx->sigmask = sigmask; 280 281 /* 282 * When we call this, the initialization must be complete, since 283 * anon_inode_getfd() will install the fd. 284 */ 285 ufd = anon_inode_getfd("[signalfd]", &signalfd_fops, ctx, 286 O_RDWR | (flags & (O_CLOEXEC | O_NONBLOCK))); 287 if (ufd < 0) 288 kfree(ctx); 289 } else { 290 struct fd f = fdget(ufd); 291 if (!f.file) 292 return -EBADF; 293 ctx = f.file->private_data; 294 if (f.file->f_op != &signalfd_fops) { 295 fdput(f); 296 return -EINVAL; 297 } 298 spin_lock_irq(¤t->sighand->siglock); 299 ctx->sigmask = sigmask; 300 spin_unlock_irq(¤t->sighand->siglock); 301 302 wake_up(¤t->sighand->signalfd_wqh); 303 fdput(f); 304 } 305 306 return ufd; 307 } 308 309 SYSCALL_DEFINE3(signalfd, int, ufd, sigset_t __user *, user_mask, 310 size_t, sizemask) 311 { 312 return sys_signalfd4(ufd, user_mask, sizemask, 0); 313 } 314